LNG LIQUEFACTION SYSTEM AND PROCESS

1 . A method for natural gas liquefaction, comprising:

providing a clean gas stream 1 and a recirculation gas stream 28 at a first pressure;

mixing the clean gas stream 1 and the recirculation gas stream 28 to form a mixed gas stream 1 A;

splitting the mixed gas stream 1 A into at least a first stream 2 and a second stream 3 ;

passing the first stream 2 through a heat exchanger 100 ;

wherein the heat exchanger 100 cools the first stream 2 to form a first liquefied stream 4 by cross exchanging with one or more refrigeration streams, wherein the one or more refrigeration streams comprise:

an expander refrigeration stream 11 ;

a secondary refrigeration stream 15 ; and

a tertiary refrigeration stream 34 ; and

cooling the second stream 3 by passing it through the heat exchanger 100 to form a cooled gas stream 5 ;

passing the cooled gas stream 5 through a turbo-expander 300 to form the expander refrigeration stream 11 ;

passing the expander refrigeration stream 11 through the heat exchanger 100 to form a first refrigeration return gas stream 12 ;

generating a first slipstream 14 from the first liquefied stream 4 and reducing pressure of the first slipstream 14 to form secondary refrigeration stream 15 ;

passing the secondary refrigeration stream 15 through the heat exchanger 100 to form a second refrigeration return gas stream 16 ;

combining the first refrigeration return gas stream 12 and the second return gas stream 16 to form a first combined stream 20 ;

generating a second slipstream 32 from the first liquefied stream 4 and reducing pressure of the second slipstream 32 to form reduced-pressure slip stream 33 ;

combining the reduced-pressure slipstream 33 with a boil off gas stream 31 from liquid natural gas storage 1500 to form the tertiary refrigeration stream 34 ;

passing the tertiary refrigeration stream 34 through the heat exchanger 100 to form a tertiary refrigeration return gas stream 35 ;

compressing the tertiary refrigeration return gas stream 35 using a first compressor 700 to form a compressed tertiary refrigeration return gas stream 36 ;

combining the compressed tertiary refrigeration return gas stream 36 with the first combined stream 20 to form a second combined stream 21 ;

compressing and optionally cooling the second combined stream 21 using one or more additional compressor(s) (e.g., 900 , 1000 , 1200 , and/or 1900 ) and optionally one or more cooler(s) ( 1100 and/or 1150 ) to form the recirculation gas stream 28 at pressure P recycle ;

reducing pressure of the first liquefied stream 4 to form a two-phase product stream 8 ; and

recycling the one or more refrigeration streams through the system until a desired cryogenic liquid storage temperature is reached.

2 . The method of claim 1 , wherein the clean gas stream 1 is free of or reduced in impurities that tend to freeze at cryogenic temperatures.

3 . The method of claim 1 , wherein the first stream 2 is cooled by the heat exchanger 100 to a cryogenic temperature.

4 . The method of claim 1 , wherein one or more of the compressing steps is performed using part of or all work extracted at the turbo-expander 300 .

5 . The method of claim 1 , further comprising monitoring one or more of flow rate, flow volume, gas temperature, gas composition, or gas pressure.

6 . The method of claim 1 , further comprising adjusting one or more of flow rate, flow volume, and/or flow ratio of one or more of the clean gas stream 1 , the first stream 2 , the second stream 3 , the expander refrigeration stream 11 , the secondary refrigeration stream 15 , and/or the tertiary refrigeration stream 34 based on the monitoring.

7 . The method of claim 1 , further comprising expanding, decreasing the pressure of, and/or cooling one or more stream by way of one or more pressure-reducing valves.

8 . The method of claim 1 , further comprising delivering the two-phase product stream 8 to a storage container once the desired cryogenic liquid storage temperature is reached.

9 . The method of claim 1 , wherein the turbo-expander 300 , and one or more compressor are part of a single system coupled via a bull gear and pinions.

10 . The method of claim 1 , further comprising serially compressing the second combined stream 21 by compression with: i) a first compressor or compression stage 900 , then ii) a second compressor or compression stage 1000 , and then iii) a third compressor or compression stage 1200 or 1900 to form the recirculation gas stream 28 .

11 . The method of claim 1 , wherein the compressing of the second combined stream 21 is performed using a compander.

12 . The method of claim 1 , wherein the compressing of the second combined stream 21 is performed using a recycle compressor package and the compression side of an expander package.

13 . The method of claim 12 , wherein the expander package comprises a compressor and expander, wherein the expander package is separate and independent from the recycle compressor package.

14 . The method of claim 12 , wherein the recycle compressor package comprises a multi-stage compressor, such as two or more stages, with a single prime mover and a single shaft.

15 . The method of claim 1 , wherein the compressing of the second combined stream 21 is performed using a multi-stage compressor system with:

i) a compression system with at least three compression stages; or

ii) a compression system with at least three stand-alone compressors; or

iii) at least two compressors each sharing a shaft with a compressor or expander; or

iv) a first compressor comprising first 900 and second 1000 compression stages sharing a first shaft and a second compressor 1200 comprising a third compression stage; or

v) a first compressor comprising first 900 and second 1000 compression stages sharing a first shaft and a second compressor 1200 sharing a second shaft with an expander, such as a turbo-expander 300 , and comprising a third compression stage; or

vi) a first stand-alone compressor 900 , a second stand-alone compressor 1000 , and a third compressor 1900 sharing a shaft with a compressor or expander, such as a turbo-expander 300 ;

or vii) a first compression stage 1900 of a compressor sharing a shaft with a compressor or expander, such as a turbo-expander 300 , a second stand-alone compressor 900 , and a third stand-alone compressor 1000 ; or

viii) a first compressor comprising first 900 and second 1000 compression stages sharing a first shaft and a second compressor 1900 comprising a third compression stage, and optionally wherein compression stage 1900 is a stand-alone compressor or compression stage 1900 is a compressor sharing a shaft with a compressor or expander, such as a turbo-expander 300 ; or

ix) a first compressor comprising a first compression stage sharing a first shaft with an expander, such as a turbo-expander 300 , a second stand-alone compressor 900 , and a third stand-alone compressor 1000 .

16 . The method of claim 9 , wherein a single motor provides all external power required to perform the method.

17 . The method of claim 15 , wherein part of or all work extracted at expander 300 is used in compressing the second combined stream 21 .

18 . The method of claim 1 , wherein the tertiary refrigeration return gas stream 35 is boosted in pressure by way of a low-pressure compressor.

19 . A method for natural gas liquefaction, comprising:

providing a gas stream 1 and a recirculation gas stream 28 ;

mixing the gas stream 1 and the recirculation gas stream 28 to form a mixed gas stream 1 A;

splitting the mixed gas stream 1 A into at least a first stream 2 and a second stream 3 ;

passing the first stream 2 and the second stream 3 through a heat exchanger 100 comprising:

an expander refrigeration stream 11 ;

optionally, a secondary refrigeration stream 15 ; and

optionally, a tertiary refrigeration stream 34 ;

wherein the heat exchanger 100 cools the first stream 2 to form a first liquefied stream 4 , which is split to form a two-phase stream of natural gas 8 , and i) optionally a first slipstream 14 , and ii) optionally a second slipstream 32 , and iii) optionally the first slipstream 14 is reduced in pressure to provide the secondary refrigeration stream 15 , and optionally the second slipstream 32 is reduced in pressure to provide reduced-pressure slipstream 33 which is optionally combined with boil-off gas stream 31 to form the tertiary refrigeration stream 34 ;

wherein the heat exchanger 100 cools the second stream 3 by passing it through the heat exchanger 100 to form a cooled gas stream 5 :

wherein the cooled gas stream 5 is passed through a turbo-expander 300 to provide the expander refrigeration stream 11 ;

wherein one or more of the expander refrigeration stream 11 , the secondary refrigeration stream 15 , and/or the tertiary refrigeration stream 34 are optionally passed through a heat exchanger 100 and are compressed one or more times, individually or together, to provide a portion or all of the recirculation gas stream 28 .

20 . A system for natural gas liquefaction, comprising:

one or more heat exchanger 100 comprising:

an expander refrigeration stream 11 ;

a secondary refrigeration stream 15 ; and

a tertiary refrigeration stream 34 ;

wherein one or more of the heat exchangers 100 comprise one or more inputs to receive one or more mixed gas streams 1 A from a natural gas stream and a recirculation gas stream;

wherein one or more of the heat exchangers is configured to cool the mixed gas streams and provide a first liquefied stream 4 and a cooled gas stream 5 therefrom;

at least one turbo-expander 300 configured to receive the cooled gas stream 5 and to provide the expander refrigeration stream 11 for input into one or more of the heat exchangers 100 ;

storage 1500 configured to receive all or a portion of a two-phase product stream 8 which has been reduced in pressure from the first liquefied stream 4 , wherein optionally the first liquefied stream 4 is split and reduced in pressure to provide for the secondary refrigeration stream 15 and/or the tertiary refrigeration stream 34 ;

wherein one or more of the heat exchangers 100 comprises one or more inputs to receive one or more or all of the expander refrigeration stream 11 , the secondary refrigeration stream 15 and/or the tertiary refrigeration stream 34 ;

one or more compressors with one or more inputs for receiving one or more or all of the expander refrigeration stream 11 , the secondary refrigeration stream 15 and/or the tertiary refrigeration stream 34 , which compressor(s) provide the recirculation gas stream 28 as an output.